The invention relates to a process for the production of a thin film optical waveguide of TiO.sub.2 with an attenuation of &lt;5 dB/cm on a planar inorganic substrate.
Thin film waveguides on planar inorganic substrates are known per se. Thus, a method for producing the waveguides by sputtering is disclosed in Sov. J. Opt. Technol. 54(l), Jan. 1987, pages 22-24. However, the waveguides described therein exhibit a very high attenuation absorption loss of up to 8 dB/cm, which is unsatisfactory under practical conditions. A similar process has been described in JP-OS 3-28832 of Feb. 7, 1991. Processes for the production of waveguides, ranging from thin film vapor deposition methods via sputtering, dipping and centrifugal processes to CVD, diffusion, ion exchange, or ion implantation methods, are described in L. D. Hutcheson, Integrated Opt. Circuits and Components, M. Dekker, Inc., New York, 1987, pages 57-69.
Although TiO.sub.2 would be well suited as a material for thin film waveguides due to its physical and chemical properties--it has a very high refractive index, good chemical stability, and is very hard--no process for the production of a low-loss TiO.sub.2 thin film waveguide is known from the literature. The apparent reason for this is that TiO.sub.2 has a very strong tendency toward crystallization during its manufacture. Since scattering occurs on crystalline surfaces, evoking a strong absorption loss, the resultant product would suffer.